Respiratory humidification systems are used in providing respiratory therapy to a patient. In general terms, the system includes a ventilator, humidifier and patient circuit. The ventilator supplies gases to a humidification chamber coupled with the humidifier. Water within the humidification chamber is heated by the humidifier, which produces water vapor that humidifies gases within the chamber. From the chamber, humidified gases are then carried to the patient through the patient circuit. Humidification chambers can employ a fluid control mechanism to prevent liquid from directly passing to the patient, as this situation can be very harmful to the patient.
Current fluid control mechanism include one or more valves that are operated in response to a level of liquid in the chamber. Single valve chambers can be prone to defects in the event of failure of the valve. As a result, some chambers employ a dual valve mechanism having a primary valve and secondary valve that operates to stop fluid from entering the chamber in the event of failure of the primary valve. Each of the valves are arranged coaxially, thus requiring an inner valve to be positioned within an outer valve. This arrangement requires a large sealing area for the outer valve as well as a relatively large force to seal the outer valve. Due to the large sealing area and large force required to close the outer valve, failure of the valve can result.